______ (introduce) a person to others is very difficult for a shy man like T______ (introduce)a person to others is very difficult for a shy man like Tom.这种题什么时候用doing什么时候用to do.
问题描述：
______ (introduce) a person to others is very difficult for a shy man like T
______ (introduce)a person to others is very difficult for a shy man like Tom.
这种题什么时候用doing什么时候用to do.
答